Portable electronic musical instrumetns



April 16, 1963 T. c. EDWARDS 3,085,460

PORTABLE ELECTRONIC MUSICAL INSTRUMENTS Filed Aug. 14. 1961 ,2- FIG. I

Amenna in Shielded Pas/flan 50 Receiver, 49 INVENTOR. i AmpII'fI'eI;Thomas 0. Edwards 1 51 5 l l Speaker United States? 3,085,460 PatentedApr. 16, 1963 3,685,468 PORTABLE ELECTRGNIC MUSICAL INSTRUMENTS ThomasC. Edwards, Los Alamos, N. Mex. (351-C, Rte. 1, Espanola, N. Mex.) FiledAug. 14, 1961, Ser. No. 131,134 2 Claims. (Cl. 84-1) This inventionrelates to a portable electronic musical instrument, i.e., one which isto be carried by a performer, and it pertains more particularly to animproved system for eliminating the external connector-cable which hasheretofore been used with such electronic musical instruments.

Although radio link sound pickups have long been known (US 2,710,345,Walkie-Talkies, etc.) electronic guitars, which are also old and wellknow, have heretofore required a cable between said guitar and aspeaker; an object of this invention is to eliminate the necessity ofsuch external cable. A further object is to provide an improvedtransmitter-power assembly for portable electronic musical instrumentswith the antenna thereof so positioned that it does not come closeenough to any part of the performers body to distort or interfere withtransmitted signals and does not protrude in a direction which mightbring it into contact or too close proximity to other performers orobjects. A further object of the invention is to provide new tone andsound effects which cannot be duplicated with cable-to-speaker systemswithout the use of expensive and complicated circuitry. Other objectswill become apparent as the detailed desription of the inventionproceeds.

Briefly, I employ a small transmitter powered by a small battery in anassembly small enough to fit into the musical instrument which providesthe source of mechanical sound vibrations. For an electronic guitar thisassembly may be about 1.5 x 2" x 3", or even smaller. A conventionaltransducer system may be employed for converting the sound vibrations toelectrical signals, but these signals are conducted within theinstrument itself to the transmitter-power assembly instead of beingconnected by an external cable to a speaker. The transmitter circuit ispreferably one which employs a tunnel-diode, i.e., is a tunnel diodeoscillator circuit, though other transmitting circuits may be used. Atunnel diode is a germanium semiconductor device described andcharacterized in detail in Tunnel Diode Manual, copyright 1961 byGeneral Electric Co., the ratings and characteristics of such tunneldiodes being set forth on pages 11 to 17, 87 and 95 of said manual;tunnel diode oscillator circuits are shown on pages "33 to 42 of saidmanual and are exemplified by the circuit on page 41 thereof using the1N2939 tunnel diode.

The transmitter and particularly the antenna thereof should be somounted as to provide shielding from too close proximity to parts of aperformers body or to external objects; nothing having a capacitanceeffect should come closer than about an inch and preferably not closerthan two inches to the antenna. By mounting the antenna on or within aguitar or other stringed instrument about 2 to 3 inches above thefretted neck and substantially parallel thereto, it is protected by theflexed left arm of the performer from external physical contacts orelectrical disturbance or drift. To avoid dead spots, a plurality ofantennas may be used, i.e., either the instrument or thereceiver-speaker may have at least two antennas spaced about one tothree feet or more apart; it is usually undesirable to have a secondantenna on the instrument and hence it is preferred that the receiver beprovided with spaced antennas.

The transmitter and receiver should of course be tuned to the samefrequency and it is desirable that a variable frequency transmittingcircuit be employed, the variation being obtainable by using a variablecondenser or by plugging in crystals of different frequency or by anyother known means. When a number of electronic musical instruments areplaying together as in a band or orchestra, each should be tuned to itsrespective receiver. A microphone may be plugged into a jack on theinstrument for transmitting the performers voice with the guitar music.

The invention will be more clearly understood from the followingdetailed description of a preferred example thereof read in conjunctionwith the accompanying drawings which form a part of this disclosure andin which:

FIGURE 1 is a view of an electronic guitar showing the position of thetransmitter and antenna with respect to the body of the performerplaying the instrument.

FIGURE 2 is a schematic diagram of the transmitter circuit showing itsrelationship with the other parts of the combination.

While an electronic guitar will be described in detail as my preferredexample, it should be understood that my invention is applicable to anyother electronic musical instrument that is carried by a performer,particularly to those characterized by vibrating strings or reeds.

Referring to FIGURE 1, performer 10 is playing an electronic guitar 11which is supported by shoulder strap 12 with end openings engagingsupporting buttons 13 and 14. The performers left hand 15 normally comesunder and around the fretted neck so that the fingers of the left handmay press strings 16 against frets 17, the lower part of the instrumentbeing curved inwardly adjacent the fretted neck to permit the fingers ofthe left hand to reach the lowermost frets. The performers right hand 18is normally above strings 16 just beyond bridge 19, the strings beingstrummed, plucked or otherwise vibrated by the fingers and/or thumb ofsaid right hand. The strings are anchored to holding plate 20 in anyknown manner, and they are tuned at the upper end of the fretted neck byany means known to the art.

Since the guitar is an electronic instrument, it is provided with theusual transducer system, which includes one or more transducers. Ipreferably employ one transducer 21 spaced about six inches from thebridge 19 and another transducer 22 spaced quite close (within an inchor so) to said bridge. Transducer systems are well known and hencerequire no detailed description. The system diagrammatically representedin FIGURE 2 includes a winding 23 around strong magnets of the permanenttype on each side of magnetic poles under each string so thatdifferences in sound vibrations cause corresponding differences inelectrical signals that are generated. Winding or inductance 23 isconnected across variable resistance 24 which is actuated by knob 24a onthe instrument to control volume. The sliding contact on resistance 24is connected through condenser 25 to the sliding contact of variableresistance 26, which is actuated by knob 26a on the instrument tocontrol tone quality. In the other transducer circuit 21', knob 27aactuates variable resistance 27 for volume control and knob 28a actuatesvariable resistance 28 for tone control. Transducer circuit 21 isgrounded at 29 and circuit 22' at 30. Switch 31, which is actuated bybutton 31a on the instrument, enables the performer to select thetransducer 21 or 22 which he desires, and this switch may be designed toenable any number of transducers to be connected in series or parallelto obtain desired sound effects. Sliding connection or jack 32. washeretofore used for plugging in a cable leading to a speaker.

With my invention no external cable is plugged into the instrument, andit may be freely moved for distances of about 2 to 25 feet or more.Internal connectors 33 and 33 lead from the transducer system A throughan opening B in the instrument itself to my improved transmitterpowerassembly C, which is in a part of the instrument remote from thetransducer system to avoid electrical disturbance and to facilitatephysical control. The transmitter portion of the assembly is preferablyatunnel diode circuit as will be hereinafter described. As shown in FIG.1, the transmitter-power assembly is mounted with in the instrumentunder a plate above the fretted neck while the transducer system isunder the so-called scratch plate at the lower part of the instrumentwhen it is in playing position. The power source may be a battery, butit may alternatively be a receiver for transmitted electrical energy,the important feature being that I do not employ any external cable orconnector leading from the instrument to a separate power source. Thetransmitterpower assembly is preferably shielded in any conventionalmanner to minimize frequency drift.

As for the tunnel diode circuit, conductors 33 and 33 are connected,preferably through an audio amplifier stage 34, to an oscillatingcircuit. Conductor 33 is connected through switch 35, battery 36 andresistance 37 to terminal point 38 and it is also connected to point 38through resistance 39. Switch 35 is actuated by button 35a on theinstrument. Connector 33' is connected to point 38 through condenser 40.Connector 33 leads to copper strip connector 41 and point 38 isconnected to copper strip 42, a condenser 43 being connected betweenstrips 4 2 and 41. A tunnel diode 44 is connected to strip 42 and toanother strip 45, a variable condenser 46 (actuated by knob 46a on theinstrument) being connected between conductor strips 41 and 45. Aninductance 47 is connected between the ends of conductor strips 41 and45, said inductance 47 cooperating with variable condenser 46 to form aso-called tank circuit. The transmitting antenna is connected toconductor strip 45. In this example the copper strips are secured to aplastic base sheet, they are about wide and very thin. The values of therespective elements in the specific example are as follows:

Element: Value Battery 36 1.5 volt mercury cell. Resistance 37 270 ohms.

Resistance 39 22 ohms.

Condenser 40 50 microfarads.

Condenser 43 0.001 microfarad.

Tunnel diode 44- G.E. 1N2939 (see tunnel diode manual).

Variable condenser 46-"- 1.5 micromicrofarads to 5.0 mmf.

Inductance 47 0.2 micro henrys.

Antenna 4-8 4.75 inches long.

The operation of the invention should be obvious from the foregoingdescription. The strings of the guitar are manually tuned as usual.Switch 311 is placed in the desired position by manipulating button 31a.Switch 35 is closed by means of button 35a. Knob 46a is set to positionvariable condenser 46 and to obtain the desired frequency, which may forexample be about 70 to 117 mc./ sec., e.g. 107 n1c./ sec. Volume andtone quality are adjusted by positioning knobs 24a and 26a and/or 27aand 28a. Thenceforth the instrument may be handled and played as if itwere an ordinary non-electronic guitar, but with a wide range of volumeand tonal effects not attainable with a simple acoustical instrument.The signal transmitted from antenna 48 is picked up by the antennae 49and 50 of receiver-speaker assembly 51 which is usually also providedwith one or more amplifying stages and which is tuned to the frequencyof the transmitter. The transmitter circuit may be tuned to a frequencyin the conventional radio broadcasting band (550 to 1700 kc./sec.) sothat the transmitted signals may be picked up by an ordinary radio andthe sound may come from the speaker thereof.

I have discovered that the tonal effects obtainable by use of mytransmitter are unexpectedly quite different under some conditions thanthose obtained when the instrument is connected to the speaker with acable. When the audio amplifier stage is used with the transmittingcircuit, it may be manually controlled by one or more knobs (not shown)on the instrument, thus giving the performer even more latitude withrespect to tone volume and sound effects.

While the invention has been described by reference to a specificexample, it is not limited thereto. Other more simple or more elaboratecircuits may be used either in the transducer system or in thetransmitting circuit. The transmitting antenna may be encased in ashielding element. The values and arrangement of the various elementsmay vary Widely as will be apparent from the above description to thoseskilled in the art.

I claim:

1. An electronic guitar having a fretted neck; a power source, avariable frequency transmitter circuit, a transducer system andconnections from the transducer system and the power source to thetransmitter circuit, all carried in said guitar; and a transmittingantenna connected tothe transmitter circuit and mounted about 2 to 3inches above said fretted neck and substantially parallel thereto sothat when the guitar is played by a performer, the antenna is protectedby the timed left arm of said performer from external physical contactsand electrical disturbance and drift, and signals may be broadcast fromsaid antenna to a receiver spaced therefrom and without any electricalconnector therebetween.

2. In combination, a portable, electronic, stringed, musical instrumenthaving a neck adapted to be held by a performers left hand curved underand in front of it and having strings adapted to be vibrated by thethumb and fingers of the performers right hand; a power source, avariable frequency transmitter circuit, a transducer system andconnections from the transducer system and the power source to thetransmitter circuit, all carried in said musical instrument; and atransmitting antenna connected to the transmitter circuit and carried bythe musical instrument about 2 to 3 inches above said neck so that it isin shielded position when the instrument is being played and so that itis protected from external physical contacts and from electricaldisturbance and drift, whereby signals may be broadcast from saidantenna to a receiver spaced therefrom and in tune with the frequency ofsaid transmitter circuit Without any electrical connector between saidmusical instrument and said receiver.

References Cited in the file of this patent UNITED STATES PATENTS2,488,927 Owens Nov. 22, 1949 FOREIGN PATENTS 1,160,069 France July 7,1958 OTHER REFERENCES The Dynatone, Radio-Craft, January 1939, 2 pages,beginning on page 398.

Transistorized Ukulele, Radio Electronics, February 1954, pages 30-32.

Electronic Banjo, Popular Electronics, February 1956, pages 6 l63, 117and 118.

General Electric Transistor Manual, 5th ed., Oct. 28, 1960, pages 163and 164.

1. AN ELECTRONIC GUITAR HAVING A FRETTED NECK; A POWER SOURCE, AVARIABLE FREQUENCY TRANSMITTER CIRCUIT, A TRANSDUCER SYSTEM ANDCONNECTIONS FROM THE TRANSDUCER SYSTEM AND THE POWER SOURCE TO THETRANSMITTER CIRCUIT, ALL CARRIED IN SAID GUITAR; AND A TRANSMITTINGANTENNA CONNECTED TO THE TRANSMITTER CIRCUIT AND MOUNTED ABOUT 2 TO 3INCHES ABOVE SAID FRETTED NECK AND SUBSTANTIALLY PARALLEL THERETO SOTHAT WHEN THE GUITAR IS PLAYED BY A PERFORMER, THE ANTENNA IS PROTECTEDBY THE FLEXED LEFT ARM OF SAID PERFORMER FROM EXTERNAL PHYSICAL CONTACTSAND ELECTRICAL DISTURBANCE AND DRIFT, AND SIGNALS MAY BE BROADCAST FROMSAID ANTENNA TO A RECEIVER SPACED THEREFROM AND WITHOUT ANY ELECTRICALCONNECTOR THEREBETWEEN.